Correct tooth alignment. Close-up of teeth after fixed braces have been removed. Braces (or ortho- dontic devices) are worn to correct malocclusions (poor alignment between upper and lower jaws) or overcrowding of teeth. Fixed braces are used when many teeth need repositioning as they give more precise control over teeth movement than removable braces. These braces consist of metal brackets cemented to each tooth, with an adjustable wire threaded through each bracket. Fixed braces make teeth cleaning more difficult as they trap dental plaque; plaque residues (brown, centre left) can be seen on the teeth. Dental plaque is a sticky coating consisting of bacteria and food debris.